Precision stress breaker for removable partial restorations



Sept. 30, 195 P. G. BAcA ET AL PRECISION STRESS BREAKER FOR REMOVABLE PARTIAL RESTORATIONS Filed April 27, 1950 JNI/E/VTORS: P446700 6. 151404 51057095 6. 5A CA Patented Sept. 30, 1952 PRECISION STRESS BREAKER FOR REMov-Y ABLE PARTIAL RESITORATIONS Placido G. Baca and Faustino G. Baca,

Los Angeles, Calif.

' Application April 27, 1950, Serial No. 158,442

Our invention relates generally to the dental art, and particularly to improvements in partial dentures. Specifically, the invention pertains to an improved connecting means, commonly referred to as a stress-breaker, by which a partial dental plate isconnected to a natural abutment tooth in a manner such that movement of the partial plate, relative to the abutment tooth, is permitted so as to avoid objectionable stress or pressure on the abutment'tooth during mastication.

It is well recognized in the dental'art that partial dentures or restorations whichreplace less than all the natural teeth of a jaw have several disadvantages which are not readily overcome. For example, it is necessary that such a partial denture be suitably anchoredor .detachably connected to a natural abutment tooth which is disposed immediately forward of that portion of the gum to which the partial plate is to be applied. It has been determined in the past that when such a plate is rigidly connected at one end to an abutment tooth by means of a clasp which is carried by the plate and which at least partially encircles the abutment tooth, the plate is, in effect, a cantilever which rests against the relatively soft gum tissue. For this reason, it is well known that during mastication the partial denture is forced in a direction toward the gum and this results not only in flexing of the plate and its clasp but imposes considerable strain on the abutment tooth which, over a period of time, may become loose in its jaw socket. In many such cases, the loosened abutment tooth becomes useless as an anchor for the partial denture and as a means of mastication and its extraction is necessitated, atwhich time the next anterior tooth is utilized as an abutment for a new partial denture or restoration which must now include a tooth to replace the extracted one.

Many expedients have been proposed for obviating the difficulty discussed above, it being common practice to provide a so-called stressbreaker device for connecting a partial denture to a natural abutment tooth in such a way that relative movement between the denture and the abutment tooth is permitted so as to relieve the strain which would otherwise be imposed on the abutment tooth during mastication. Many forms of stress-breakers have been proposed for accomplishing the desired result, such devices usually including a socket member carried by the partial denture, and a support member detachably connected to the abutment tooth by means of an integral clasp, and having an end disposed in the socket member. By this construction.

13 Claims. (01. 32-4) vertical sliding movement of the socket member with respect to the relatively stationary support member is permitted when the partial denture is pressed against the soft. gum tissue durin mastication so that strain on the abutment tooth is'minimized. The result is also attained by providing a stress-breaker connection which embodies a socket member on the partial denture and a ball or other similar element detachably connected to the abutment/tooth and adapted to swivel within the socket member, this construction resulting in a pivotal action of the denture with respect to the abutment tooth. In still ariother form of stress-breaker, the. relatively stationary element isso' connected to the socket member that a combined vertical sliding movement and pivotal action is effected.

Such prior stress-breaker devices are subject to various disadvantages. In the first place,

when the device is constructed to allow only straight vertical movement, the delicate components thereof are themselves subjected to considerable stress, this being due largely to a'.bending moment imposed against these parts, particularly when food is masticated at the posterior end of the partial denture... As might be expected, distortion of the stress-breakercomponents results in a loose connection which is .very objectionable. When a' stressebreaker device .of the pivotal type is employed, the posterior or distal end of the partial denturemay haveunrestricted, substantially vertical, movement while the range of vertical movement at. the anterior end of the denture is very limited. so that strain may be imposed upon the abutment tooth. Such a pivotal connection also allowstransverserocking motion of the partial denture and'this is highly objectionable. A stress-breaker deviceoperating uponthe combined vertical and pivotal movement principle'has been considered more practical but such a device is subject to the'same disadvantages, to a lesser degree. I

It frequently occurs that a partial denture is applied to use at eachside of a jaw and in such cases the dentures are; connected by; a curved lingual bar which is connected to and extends between the anterior ends or the dentures at the rearwardv side of the frontal portion of the gum and the natural teeth thereof. The lingual bar is intended to rest lightly, against the gum and it is imperative, that pressuref'of the bar or sliding movement thereof against the gum be prevented if irritation of the gum is to be avoided. It has been found that such impingement of the lingual bar cannot be overcome by the use of any of the stress-breaker devices discussed above for the reason that the vertical or pivotal movement, or both, imparted to either partial denture during mastication is communicated directly to the lingual bar to cause the latter to press into a rub along the gum, and this results in considerable discomfort to the wearer.

It is a primary object of our invention to obviate the deficiencies of prior dental stressbreaker devices discussed above by providing a stress-breaker which eifects movement of a partial denture in a path which extends obliquely in a posterior direction with respect to the abutment tooth to which the denture is anchored. By this provision, the partial denture is caused to bear against the gum tissue with uniform pressure throughout its length so as to provide greater comfort for the wearer. Moreover, since the movement of the partial denture is restricted to such an oblique path, true pivotal movement thereof is prevented so that impingement of the anterior end of the denture against the abutment tooth and the gum tissue surrounding the same is eifectively avoided. Furthermore, since the denture moves away from the horizontal plane of the teeth of the jaw and posteriorly during mastication, it follows that a lingual bar connected thereto must also move in a like path to cause it to substantially follow the contour or profile .of the gum to prevent impingement or rubbing of the lingual bar against the gum, this highly desirable result being attained when either .or both dentures of a pair of dentures located at either side of the jaw are utilized during the mastication process.

Another object of the invention is to provide a dental stress-breaker which is very simple in construction, the device comprising a slide member of channel shape suitably joined to the anterior end of the partial denture and a support bar of rectangular cross section having an integral clasp portion by which the bar is detachably connected to the abutment tooth and provided with an elongate opening extending in a direction away from the horizontal plane of the teeth of the jaw and posteriorly with respect to the abutment tooth, said support bar being receivable in the slide member, the device further including a connecting means, consisting of a screw, pin or the like, carried by and an tending between the side walls of the slide member and through said elongate opening. By this construction, the partial denture is connected to the abutment tooth and movable with respect thereto in a path extending away from the horizontal plane of the teeth of the jaw and posteriorly of the abutment tooth for the purpose previously explained. A related object is to provide a stress-breaker device in which the slide member is carried by the saddle of the denture and is embedded in the material of the partial denture. Another object is to provide a device of this character in which the connecting means consists of a screw having a shank passing through an aperture in the inner side wall of the slide member and through the elongate opening of the support bar member, said screw having a threaded end screwed into a threaded hole in the outer side wall. By this means, the connecting screw is inserted from the inner side oi the partial denture and is therefore concealed from view.

Another object is to provide a dental stressbreaker of the type indicated in which there exists minimum clearance between its relatively 4 movable components so that the presence of crevices or cavities, in which particles of food may lodge, is avoided. A related object is to provide such a stress-breaker which, due to the closely fitting slide and support bar members, prevents transverse rocking of the partial denture.

A further important object is to provide a dental stress-breaker which is self-adjusting so as to allow the partial denture to normally rest lightly against the gum tissue to provide a comfortable fit, this feature enabling the partial denture to adjust itself to the contour of the gum tissue to compensate for shrinkage of the tissue.

A still further object is to provide a dental stress-breaker which is composed of a minimum number of parts each adapted for economical manufacture from precious alloys. A related object is to provide a device of this character, the major parts of which may be made from plastic -to serve as male patterns for forming cavities or matrices in which the parts may be cast from selected alloys.

Further objects of the invention will appear from the following description, and from the drawing, which is intendedfor the purpose of illustration only, and in which:

Fig. 1 is a perspective view of a pair of our improved dental stress-breaker devices, showing them applied touse in connecting a pair of partial dentures toabutment teeth of the lower jaw of a person;

Fig. 2 is an enlarged plan view of one of the partial dentures and one of the improved stressbreaker devices, as applied to the left-hand side of the lower jaw;

Fig. 3 is a side elevationalview of the same, asviewed in the direction ofthe arrow 3 in Fig. 2-, the partial denture being illustrated in its normalposition, prior to a mastication process;

Fig. 4 is a view similar to Fig. 3, with certain components shown in section, the partial denture being. illustrated in the depressed position assumed thereby. during the mastication process; and

Fig. 5-is a cross-sectionalview, taken on line 55 of Fig. 3.

Referring to the drawing in detail, our iinproved dental stress-breaker devices it! are shown as applied touse in connecting a pair of partial dental restorations or dentures ii to natural abutment teeth 2 at the opposite sides of the lower jaw l3 of aperson. Since the stress-breaker devices are alike, except that they are of opposite hand, only the device id employed at the left-hand side of the jaw will be described at this point. 1

The partial denture H usedat the left-hand side of the jaw i3 may be more or less conventional in structure, and may consist of a saddle 55 of inverted channel shape made from any suitable material, such as a moldable acrylic plastic material. Artificial teeth 26 are molded into the top of the saddle i 5 in the usual manner, and a retention element i? is also embeddedin the plastic materialduring molding of the saddle.

When the partial restoration includes a pair of the partial dentures, as illustrated in Fig. l, the retention elements I! of each partial denture are connectedby a curved lingual bar 18 which has its ends suitably joined to the forward or anterior ends or" the elements, the bar following the contour of the dental arch or, in other words, the shape of the inner surface of the gum at the linawe gual side of the frontal teeth and in close association therewith. 'In prior dental .work, it. has

been customary to provide means by which transmittal of movement of one of the partial dentures to the other partial denture is prevented, such an expedient ordinarily consisting in either making the lingual bar in two relatively movable" sections or in providing universal connecting means at the joinder of the ends of a one-piece lingual bar and the anterior ends of the denture saddles. In the former case, the relatively movable sections providev crevices in which food particles may lodge and in which the tongue may catch, and in the latter case, the universal connections weaksection, the member having an inner side wall 2 l,'

an outer wall 22 and a, posterior end wall 23. The slide member 20 may be formed integrally with the retention element IT or may be made as a separate entity and suitably joined to the element. The walls 2t, 22 and 23 definebetween them an open-topped channel or guideway 25, the longitudinal axis of which extends obliquely in an upward andforward direction from the retention element l'|. The slide member 20 is embedded in the plastic material of the partial denture saddle i5. The upper portion of the retention element ll provides a bottom wall 2'6 for the slide member 20 and this wall may have an arcuate upper surface as shown in Fig. 4.

The stress-breaker device also includes asup- 6 Fig. 4 is especially suitable for the purpose, although-itiswithin the contipti of the invention toiemploy a pin orother"means, if, desired. The

screw 35 has ashank portion133'which passes through a. holefi'n Ithe inn'e'rfside wall 2| of the slide member and through thejelongate opening 4 34 of the support bar member, thescrew having a tapered head 31- adapt'ed to seatv in a countersunk portion of the hole of, the side wall 2 I; The end'38 of the screw reduced. in diameter and isthr'eaded' to adapt it tobe screwed into athreaded'aperture in the outer side wall 22 of fth'e slide member. It is thus seen that the connecting screw 35 is inserted from the inner or lingual sideof the partial denture and this-is concealed from view'fro'm the exterior of {.the mouth. If, for any reasonit' is desired to disassemble the stressbreaker device, this maygbef readily accomplished by merely removing the Assuming. thatthe stress breake'r. devices it ar'ein place in the mouth, as shownin Fig. 1, and

that food is being masticate'df by the teeth at the left-hand side of the mouth'jas pressure is applied against the left-hand partial denture I lj'the latter is depressed and this ismade' possible by the compressibility of the soft gum tissue therebeneath. As the partial denture I l is thus force-d downwardly, the slide member'20 carried thereby is alsodepressed. Due to the inclinationjof the elongate opening 34 in the fixed support bar member 30, the connecting screw 35 is caused to "move downwardly and posteriorly therein so that port bar member 30 which has a rectangular cross-sectional shape of a size to adapt it tobe received in the channel 25 of the slide member 20 with a snug but free sliding fit. The member 30 is formed integral with or attachedto a clasp element 3! which is shaped to partially encircle the abutment tooth 12, such a clasp being conventional and being made to fit the particular case.

from its point of attachment to the clasp element 3i at the same angle as the inclination of the channel 25, and the lower end of the member is rounded. At the rear of the bar member 30 is a stop face or shoulder 32 which engages a similar face or, shoulder 33 on the inner surface of the wall 23 defining the rear boundary of the guideway 25. The support bar member 30 is provided with a long-itudinally-extending elongate opening 34 extending in the same general direction as the longitudinal axes of the 'guideway 25 and the bar member 30. Atthe top ofthe support bar member 3B is a head 34a overlying the top of the guideway 25 in closing relationship, the bar member 30 depending from this head to leave flanges shaped to conform to and normally in contact with the terminal edges of the walls 2|, 22 and 23, as suggested in Figs. 3 and 5, to limit the movement of the denture in a direction toward the opposite jaw. A shelf 34?) of the head 34a may overlie a portion of the abutment tooth I2.

The bar member 30 may be retained within the slide member 20'by various connecting means and we have found "that the screw 35 shown in,

The bar member 30 and its longitudinal axis extend obliquely downwardly and posteriorly a similar movement is imparted to the partial denture H. Itwis to be noted atthis point' that the length of the elongate opening 34 is such that, the permissible downward movement of the partial denture is very slight, being on the order of approximately .040 inch, and that the rearward component of movement is a small per cent of said downward movement. During the depression of the partial plate, I I, the-shoulder 33 of the slidemember 20 may engage the shoulder 32 of the 'supportloar member 30 to limit the downward movement of the partial denture with respect to the abutment tooth l2.

Due to the downward movement of thepartial denture I I, relative to the support-bar member 30, a bending moment of the partial denture about the abutment tooth l2, which would occur if the forward end of the denture was secured fast thereto, is entirely avoided so that the abut ment tooth is not subjected to a stress which i might tend to loosen the same from its socketin the jaw; It is to be particularly noted thatb'y the improved construction of the stress-breaker device pivotal movement of the partial denture is possible at all times and this has the advantage of allowing either end of the denture to depress to a greater extent than the other end thereof,

depending upon which end is subjected togreater pressure during the mastication processv and upon the degree of shrinking of the gum tissue beneath the denture. By trimming the shoulder 33 and extending the elongate opening 34, the extent of movement of the partial denture can be increased to meet the requirements.

Due to the rearward or posterior component of i I movement of the partial denture ll during the depression thereof, pressure of the anterior end of the partial denture ll against the abutment tooth 12 or against the gum tissue adjacent the same is relieved so, that any tendency to loosen theabutment tooth is avoided. Of equal importance i's'thef fact that during'the depression of the partial denture and the slight posterior move- 7 ment thereof, the lingual bar I8 is drawn rearwardly so that pressure thereof against the gum tissue at the rear of the frontal teeth is relieved.

By this provision, abrasion of the gum tissue, by

either frontal pressure or vertical sliding movement of the lingual bar thereagainst is wholly avoided and maximum comfort for the wearer is assured. When the mastication process is effected only by one partial denture, only that end of the lingual bar which is connected to that particular denture may be drawn rearwardly but when both partial dentures are active, the entire lingual bar is displaced in the posterior direction.

Thus far, our improved stress-breaker device has been described-as adapted for use in conmotion with a partial denture applied to an abutment tooth of the lower jaw. The device is, however, equally adaptable for use in connection with partial dentures applied to an upper jaw.

In such case, the elongate opening 34 extends upwardly and posteriorly with respect to the abutment tooth so that during mastication of food the partial denture is forced upwardly and rearwardly while being free to pivot slightly, so as to avoid strain on the abutment tooth and prevent pressure of the partial denture thereagainst.

It will be observed from the foregoing that our improved stress-breaker device is simple in construction and highly 'eificient in performing its intended function. As pointed out in considerabledetail, the device is so constructed and connected between the partial denture and an anterior abutment tooth that the denture is caused to move obliquelyiina direction away from the horizontal plane of the teeth of the jawancl posteriorly of the abutment tooth. By this means, the abutment tooth is relieved of all stresses which are ordinarily transmitted theretoby movement of the partial denture when the latter is rigidly connected to the abutment tooth or joined thereto by stress-breaker devices heretoforeemployed. As an important consideration, posterior movement of the partial denturerelievespressure of the lingual bar against thelgum tissue and this adds greatlyfto the comfort of the wearer by avoiding an abrasive action. In addition, ,by the use of our improved stress-breaker device, the partial denture may .pivot slightly so that the denture is in effect, self adjusting to the contour of the gum. This action, together with the oblique movement of the partial denture permits the same to move toward and away from the jaw to compensate for shrinkingor swelling of the gum tissue and thus provide a comfortable fit at all times. 7

It will be apparent to one skilled in the art that various modifications might'be made in the construction without departing .from the spirit of the invention. Consequently, we do not wish to be limtied in this respect but desire to be alforded the full scope of the appended claims.

We claim as our invention:

'l. A dental connectionfor use'in connecting a partial dental plateto'a natural abutment-tooth of a jaw at the posterior side thereof, comprising: a slide member secured to'the partial plate at the anterior end thereof, said member being of channel shape and defining a guideway having side walls and a posterior wall, said guideway being inclined with respect to the vertical and sloping obliquely from the horizontal plane of the teeth of the jaw and in a posterior direction from said anterior end'of' said plate; a support bar member adaptedto' be detachably connected to the abutment tooth, said bar member being disposed in said guideway and having a longitudinal sliding fit therein, one of said members having an elongate opening also sloping obliquely from said horizontal plane of the teeth in a posterior direction; and a connector element carried by the other of said members and extending transversely through said elongate opening of said one member so as to allow up and down but obliquely-guided movement of said partial plate relative to said bar member in a path extending obliquely away from the horizontal plane of the teeth of the jaw and posteriorly with respect to the axisof the abutment tooth.

2. A stress-breaker for use in connection with I a natural abutment tooth and a partial plate mounted posteriorly of said abutment tooth, comprising: a slide member carried by said plate at the anterior end thereof; a support bar member adapted to be detachably connected at its anterior side to said abutment tooth; and interengaging means on said barmernber and said slide member connecting said members and sloping posteriorly toward the jaw to provide a sliding movement of said slide member with respectvto said bar member in a path extending obliquely away fromthe horizontal plane of the teeth of the jaw and in a posterior direction to move said partialplate posteriorly away from said abutment tooth as said partial plate is depressed toward the jaw by mastication pressure.

3. A dental stress-breaker for use in connecting a gum-engaging tooth-holding denture to a natural abutment tooth in a space adjacent such abutment tooth, said stress-breaker comprising: a first member secured to said denture; a second member adapted to be secured to said abutment tooth, one of said memberscomprising a slide member having an open-topped guideway having a central plane substantially parallel to the axis of said abutment tooth and substantially in the line of said teeth, the other of said members comprisinga support bar longitudinally slidable in said guideway and having an elongate opening sloping posteriorly away from said axis of said abutment tooth in a direction toward the gum; and a connector element carried by said one of said members and extending substantially transversely of said central plane and through said elongate opening, said elongate opening and said connector element guiding said denture to move posteriorly away from the abutment tooth as mastication pressure depresses said denture relative to the gum it engages.

'4. A dental stress-breaker for use in connecting a gum-engaging tooth-holding denture to a natural abutment tooth in a space adjacent such abutment tooth, said stress-breaker comprising: a slide member carried by said denture at the anterior end thereof, ,said slide member defining an open-topped guideway having a central plane substantially'in' the plane of the axes ofsaid abutment tooth and the tooth of said denture; a support element adapted for connection to said abutment tooth and providing a bar member extending 'slidably in said guideway through the open top thereof, one of said members providing a wall-bounded elongate opening sloping posteriorly toward the gum and relative to the axis of said abutment tooth; and a connector element carried by the other of said members and extending through said elongate opening, said connector element engaging the walls of said-elongate-opening to guide said denture to move posteriorly away from the abut- 9 ment tooth as gum-compressing pressure is applied to said denture and because of said posterior slope of said elongate opening.

5. A dental stress-breaker as defined in claim 4 in which said support element provides a head extending across the open end of said guideway in closing relationship therewith.

6. A dental stress-breaker as defined in claim 4 in which said slide member provides walls bounding said guideway on at least three sides, said walls having edges facing away from the gum which carries said abutment tooth, and in which said support element provides a head having flanges extending beyond the periphery of said bar member to overlie said edges of said walls.

7. A dental stress-breaker as defined in claim 6 in which said flanges provide lower surfaces engageable with said edges of said walls to limit the movement of said denture relative to said abutment tooth in one direction.

8. A dental stress-breaker for use in connecting a gum-engaging tooth-holding denture to a natural abutment tooth in a space adjacent said abutment tooth, said stress-breaker comprising: a slide member carried by said denture at the anterior end thereof, said slide member having a guideway open anteriorly on the posterior of said abutment tooth and providing an open top, the sides of said guideway being closed by side walls and the posterior of said guideway being closed by a posterior wall extending between said side walls; a support element adapted for connection to said abutment tooth and providing a head extending across said open top of said guideway and a bar member depending through said open top and shaped to slide up and down relative to said guideway; and means for pivotally connecting said bar member and said slide member at a position within said guideway to swing about an axis substantially perpendicular to a plane joining said abutment tooth and the adjacent tooth of said denture, said means including means providing a limited up and down movement of said slide member relative to said bar member and means for limiting the pivoting of said slide member relative to said bar member to limit the movement of said denture away from the gum.

9. A dental stress-breaker for use in connecting a gum-engaging tooth-holding denture to a natural abutment tooth in a space adjacent said abutment tooth, said stress-breaker comprising: a slide member carried by said denture at the anterior end thereof, said slide member having a guideway open anteriorly on the posterior of said abutment tooth and providing an open top, the sides of said guideway being closed by side walls and the posterior of said guideway being closed by a posterior wall extending between said side walls; a support element adapted for connection to said abutment tooth and providing a head extending across said open top of said guideway and a bar member depending through said open top and shaped to slide up and down relative to said guideway; and means for pivotally connecting said bar member and said slide member at a position within said guideway, said means including means providing a limited up and down movement of said slide member relative to said bar member and means for limiting the pivoting of said slide member relative to said bar member to limit the movement of said denture away from the gum, said last named means including a stop shoulder on said posterior wall 10 facing anteriorly and engageable with a posterior edge of said bar member.

10. A stress-breaker as defined in claim 9 in which said posterior wall provides a guidewaybounding surface facing anteriorly and traversing a plane joining the axes of said abutment tooth and the tooth of said denture, said bar member lying substantially in said plane, said guideway-bounding surface extending in a direction toward the gum and which direction diverges posteriorly from the axis of said abutment tooth, said bar member providing a posterior edge engaging said surface, said means for providing a limited up and down movement of said slide member relative to said bar member including means for limiting such relative movement to said direction diverging posteriorly from the axis of the abutment tooth.

11. A stress-breaker as defined in claim 8 in which said means for pivotally connecting said bar member and said slide member and for providing said limited up and down movement thereof includes an elongate opening in said bar member extending in a direction toward the gum which diverges posteriorly from the axis of said abutment tooth, and a removable connector element extending through at least one of said side walls and through said elongate opening.

12. A dental stress-breaker for use in connecting a gum-engaging tooth-holding denture to a natural abutment tooth in a space adjacent such abutment tooth, said stress-breaker comprising: a first member adapted to be secured to said denture; and a second member adapted to be secured to said abutment tooth, one of said members comprising a slide member having an opentopped guideway bounded on at least three sides by wallsvincluding side walls and an end wall connecting such side walls, said guideway sloping toward the gum in a direction away from the axis of the abutment tooth, the other of said members comprising a bar longitudinally slidable relative to said guideway, said members providing engaging surfaces guiding the relative movement of said bar and said guideway so that this relative movement is in said direction sloping toward the gum and away from the axis of said abutment tooth to displace said denture away from the abutment tooth as mastication pressure depresses said denture relative to the gum it engages, said end wall comprising one 01' said engaging surfaces.

13. A dental stress-breaker as defined in claim 12 in which said engaging surfaces comprise also the bounding walls of an opening and the peripheral wall of a pin extending into said opening, said opening and said pin being respectively parts of said members, said opening being elongated in said direction away from the axis of said abutment tooth.

PLACIDO G. BACA. FAUSTINE G. BACA.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,347,555 Reese July 27, 1920 1,366,058 Chayes Jan. 18. 1921 1,480,549 Emerson Jan. 15, 1924 1,700,124 Eggen Jan. 29, 1929 2,279,351 Skinner Apr. 14, 1942 

